The present invention relates to a power aggregate, comprising:
a body,
an internal combustion engine with at least one engine cylinder mounted on the body,
a reciprocating engine piston in the engine cylinder,
a piston rod fastened to the engine piston to be reciprocated therewith, and
a pump output unit, comprising a pump cylinder and a pump piston which is fixed to the piston rod.
This type of power aggregate is disclosed in U.S. Pat. No. 3,089,305. This type of power aggregate offers a plurality of advantages over the available power aggregates in which the pump and the engine are independent units and a rotating engine crankshaft must be connected through the intermediary of a rotating power output shaft to a rotating pump transmission shaft.
Such advantages include:
an essentially simpler and more compact design since rotating components are eliminated and the engine and the pump provide structurally and functionally a single unit,
avoiding the problems involved in linking together an engine and a separate pump, and
the engine power contributes more effectively than before directly to the pressurization of hydraulic fluid.
Despite these essential advantages, however, the above type of power aggregate has not advanced beyond a testing stage. One important reason for this seems to be that there is no successful solution to power output and distribution to service points. If a piston rod is provided with just one concentric hydraulic cylinder, a problem will be how to control its output within sufficiently wide limits and how to distribute it to different service points with mutually independent power demands.